The present invention relates to detection technology, and more specifically to detection technology that is used to detect a semiconductor wafer.
Semiconductor wafers are processed within automated fabrication tools comprising a plurality of chambers. FIG. 1A is a schematic top plan view, in pertinent part, of an automated semiconductor device fabrication tool 11. The exemplary fabrication tool 11 of FIG. 1A comprises a first transfer chamber 13 and a second transfer chamber 15. A first and a second wafer handler 17, 19, each having a blade (not shown) that may support a wafer, are housed in the first transfer chamber 13 and the second transfer chamber 15, respectively. The first transfer chamber 13 and the second transfer chamber 15 are both monolithic and have various chambers coupled thereto.
A pair of loadlocks 21, 23 and a pair of pass-through chambers 25, 27 are coupled to the first transfer chamber 13. Other chambers such as degassing or oxide-etch chambers (shown in phantom) also may be coupled to the first transfer chamber 13. The pass-through chambers 25, 27 and a plurality of processing chambers 29, 31, 33, and 35, which are configured to perform various semiconductor device fabrication processes (e.g., chemical vapor deposition, sputter deposition, etc.), are coupled to the second transfer chamber 15. A controller 36 controls wafer transfer and processing within the fabrication tool 11.
Typically the environment of each chamber must be selectively isolated from the environments of neighboring chambers to prevent cross contamination, and to enable the various chambers to be maintained at pressures that differ according to the process to be performed therein. To achieve such selective isolation, each chamber is provided with a slit (not shown) through which one of the wafer handlers 17, 19 may extend to transport wafers to and from the chamber. The slit of each chamber is selectively sealed with a door assembly 37 (typically referred to as a slit valve for vacuum applications, and as a gate valve for non-vacuum applications).
As the wafer handlers 17, 19 transport a wafer through slits and through various chambers, the wafer must be accurately positioned on the blade of each wafer handler 17, 19 to avoid breaking or damaging the wafer (by the wafer falling or striking a chamber component), to ensure proper placement of the wafer on a wafer pedestal so as to prevent deposition of material on the wafer pedestal during processing and to ensure complete coverage during deposition of a material layer on the wafer, etc. Accordingly, to ensure accurate wafer positioning (so as to avoid wafer damage/breakage or deposition on a wafer pedestal, so as to ensure complete material layer coverage on a wafer, etc.), numerous wafer detection devices (e.g., sensor systems) exist in fabrication tools to determine a wafer""s position. Such sensor systems are typically located in the transfer chambers 13, 15, although sensor systems may be located in other chambers as well. A fabrication tool may employ multiple sensor systems.
Two main types of sensor systems are conventionally used within fabrication tools. Both systems employ sensors to detect a wafer""s position as the wafer enters and/or leaves a chamber. In the first system, a sensor is mounted to the outside of a processing chamber and monitors wafer position via a quartz window formed in the processing chamber. That is, a wafer is observed through the quartz window as the wafer enters and exits the processing chamber. In the second system, a sensor is mounted within a transfer chamber and monitors a wafer""s position as the wafer enters and exits the transfer chamber. The two conventional sensor systems may be used individually or jointly in the fabrication tool 11.
Both types of sensor systems have disadvantages. With regard to the first sensor system, material may deposit on the quartz window during processing and affect sensor resolution/accuracy. With regard to the second system, sensor mounting locations typically must be machined within the transfer chamber (e.g., a potentially difficult and time consuming process).
FIG. 1B is a partially exploded perspective view of the transfer chamber 15 of FIG. 1A that is useful in explaining another conventional sensor system. The transfer chamber 13 of FIG. 1A may be similarly configured.
As stated, in one conventional sensor system, a sensor may be mounted within a transfer chamber and monitor a wafer""s position as the wafer enters and exits the transfer chamber. For example, in FIG. 1B, a plurality of light transmitters 39a-b (shown in phantom) are mounted to a lid 41 of the transfer chamber 15 (e.g., to one or more quartz windows or viewports not shown) and generate light beams 44a-b (shown in phantom) that are directed toward a bottom 43 of the transfer chamber 15. A plurality of receivers 45a-b (e.g., photodetectors) are mounted to the bottom 43 of the transfer chamber 15 (e.g., the bottom 43 is machined to accept the receivers 45a-b), and are positioned to receive the light beams 44a-b generated by the transmitters 39a-b. 
By monitoring when the light beams 44a-b are broken by a wafer W positioned on a blade B (shown in phantom) of the wafer handler 19 (e.g., as the wafer W is positioned for entry through a slit 47 of the transfer chamber 15 and/or as the wafer W travels through the slit 47 of the transfer chamber 15), the position of the wafer W on the blade B may be determined by conventional techniques.
A reflection based system wherein light beams 44a-b are reflected off of the wafer W toward the receivers 45a-b also may be employed to determine wafer position (e.g., if both the transmitters 39a-b and the receivers 45a-b are mounted to either the lid 41 or the bottom 43). In either case, machining of one or more of the lid 41 and the bottom 43 may be required.
In one conventional system termed an on-the-fly (OTF) center finder, the transmitters 39a-b and the receivers 45a-b are employed to sense the wafer W as the wafer handler 19 rotates, and to determine wafer center information based thereon. Typically three light transmitters and three receivers are employed. The three light transmitters conventionally are mounted to the bottom 43 of the transfer chamber 15, outside the transfer chamber 15. Holes are machined in the bottom 43 to allow the light beams from the transmitters to travel into the transfer chamber 15. The three receivers typically are mounted to the lid 41, outside the transfer chamber 15. Holes are machined in the lid 41 to allow the light beams from the transmitters to travel to the receivers.
In operation, the OTF center finder monitors (via the receivers mounted to the lid 41 of the transfer chamber 15) when light beams emitted by the transmitters mounted to the bottom 43 of the transfer chamber 15 are blocked by the wafer W (e.g., as during such time periods, no light beams are detected by the receivers mounted to the lid 41). A corresponding xe2x80x9cblockedxe2x80x9d light beam signal is sent to a controller (not shown), and the controller determines a step count of a motor (not shown) that rotates the wafer handler 19. The controller then employs an algorithm to determine the center of the wafer W in relation to the center of the wafer handler 19. The wafer W thereby may be placed in an exact location as it travels through the slit 47.
As well as requiring machining of holes in the transfer chamber 15, the OTF center finder suffers from other drawbacks. For example, the wafer W may move on the blade B during rotation (after passing the light beams 44a-b). Wafer position determinations thereby may be inaccurate.
Accordingly, an improved method and apparatus is needed for detecting wafer position during wafer transfer.
In accordance with a first aspect of the invention, a valve/sensor assembly is provided that includes a door assembly. The door assembly has (1) a first position adapted to seal an opening of a chamber; (2) a second position adapted to allow at least a blade of a substrate handler to extend through the opening of the chamber; and (3) a mounting mechanism adapted to couple the door assembly to the chamber. The valve/sensor assembly also includes a sensor system having a transmitter and a receiver adapted to detect a presence of a substrate and to communicate through at least a portion of the door assembly.
In a second aspect of the invention, a valve/sensor assembly is provided that includes a door assembly having (1) a first position adapted to seal an opening of a chamber; (2) a second position adapted to allow at least a blade of a substrate handler to extend through the opening of the chamber; and (3) a mounting mechanism adapted to couple the door assembly to the chamber, the mounting mechanism having a viewport. The valve/sensor assembly also includes a sensor system having a transmitter and a receiver adapted to detect a presence of a substrate and to communicate through the viewport of the mounting mechanism.
Systems, methods and computer program products are provided in accordance with these and other aspects of the invention. Each computer program product may comprise a medium readable by a computer (e.g., a carrier wave signal, a floppy disk, a compact disk, a hard drive, etc.).
Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings.